Im trying to help a buddy of mine out and I am out of ideas. He has a 99 chevy silverado 4.3 4wd 5 spd with a rough idle problem. Heres the scoop, he was driving and all the sudden it started to sputter and try to die, I immediately thought fuel pump because when Ihit the gas it wouldnt get any power. The SES light was on so I pulled codes and got a random cylinder misfire so again I thought of fuel pump. He told me that he had gotten gas from his dads farm, so then we thought bad batch of gas because the truck would still run. So we changed the fuel filter, got some gas treatment, and filled up the tank with good gas. Still runs bad. Upon driving the SES started flashing and then it would illuminate and then flash again, so I thought ok Class A misfire catylist damage, so I got under the truck to look for any physical damage and noticed that he had one new cat and one stock one. I banged on the cats to see if there was anything rattling in the inside and there was a little in the new one and nothing in the old one. Ok from here Im out of ideas, please help! Thanks!

akohnz

 

I'd pull the spark plugs to see if they're fouled from the bad juice. I don't have an answer about the cats, tho.

 

Would the bad gas foul out all the plugs at once?

akohnz

 

I guess it could but pull a couple easy ones up front and see what they look like. Once they get crappy it's time just to change 'em.

 

I cant find my 5/8 plug socket so I guess I gotta wait till tomorrow to get one from my tool box at work, naturally. Thanks for the reply!!!

akohnz

 

Naturally. When I tried to change my plugs I got to the 7th and my ratchet broke - busted the gears in it. Of course, ya can't drive it with no plug in it, so had to get a ride to go buy a new d@mn ratchet.

DON'T BUY CHEAP TOOLS - you don't have to buy the best, but don't buy the cheapies.

 

I got a set of el cheapo SAE deep well sockets, 1/4" drive ratchet,SAE wrenches a flathead,phillips head screw driver,spark plug socket,vice grips,2 Bic lighters,a flash light and my registration in the glove box lol I don't carry a tool box with me in the truck and they are el cheapo in case it gets broken into.Also have jumper cables,old dizzy cap and rotor,fuel filter, as well as 4 ok condition spark plugs and my old plug wires with 4 quarts of 10w40 ,2 quarts tranny fluid,1 bottle of power steering fluid and a BIG bottle of brake fluid behind the seats.Oh an theres the spare tire,jack and lug wrench.I don't like other people working on or screwing up my truck and I damned sure don't want to pay for a tow,if you can't tell =] Sorry,ya'll got to talkin tools and I couldn't resist.I'll stfu now.

 

Well, I pulled plugs and it looks like the right bank is a little black, but other than that looks pretty normal. The left bank has some tan deposits indicating oil burning, but there are no signs of leaks internally or externally. Im still going with the idea that the gas is bad, any ideas on how to flush it out of the system? The tank is full so its gonna be a pain to drop it. Thanks for all the help!

akohnz

 

Can you get a hose into the tank?If so you can siphon it out.I personally don't care and would just use a straight hose and do it that way but you might want to get a kerosene pump style siphon and add a length of hose to get it in the tank.Gas don't make a good mouthwash.Get it all cleared out, fill it up and run a fuel treatment through it.If the gas was that bad/dirty you may want to do the fuel filter to be safe.Just a thought.

 

When I got a batch of bad gas I just taped into the fuelrail at the fitting with a fuel pressure measurement tool and a drainhose attached to it and let the truck idle in the driveway and pumped all the fuel into the old gas cans. I disposed of it in the wife's old wore out 1995 Ford Explorer a little at a time. It wasnot true bad gas, but a highly concentrated batch of alcohol based gasoline. I justran about 5 to 10 gallons of it at a timeand topped it off with a good tank of gas. Ran good in her Explorer... plus less sensors to interfer with and cleaned something out.That was 32 gallons of that bad gass and in a 55 gallon can for 2 or 3 years (marinating the stuff)before i disposed of it going down the freeway.